Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
  • B01D61/36—Pervaporation; Membrane distillation; Liquid permeation
  • B01D61/364—Membrane distillation
  • B01D61/3641—Membrane distillation comprising multiple membrane distillation steps
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D1/00—Evaporating
  • B01D1/0011—Heating features
  • B01D1/0029—Use of radiation
  • B01D1/0035—Solar energy
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D1/00—Evaporating
  • B01D1/0011—Heating features
  • B01D1/0058—Use of waste energy from other processes or sources, e.g. combustion gas
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D1/00—Evaporating
  • B01D1/28—Evaporating with vapour compression
  • B01D1/2881—Compression specifications (e.g. pressure, temperature, processes)
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D5/00—Condensation of vapours; Recovering volatile solvents by condensation
  • B01D5/0003—Condensation of vapours; Recovering volatile solvents by condensation by using heat-exchange surfaces for indirect contact between gases or vapours and the cooling medium
  • B01D5/0012—Vertical tubes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D5/00—Condensation of vapours; Recovering volatile solvents by condensation
  • B01D5/0057—Condensation of vapours; Recovering volatile solvents by condensation in combination with other processes
  • B01D5/006—Condensation of vapours; Recovering volatile solvents by condensation in combination with other processes with evaporation or distillation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D5/00—Condensation of vapours; Recovering volatile solvents by condensation
  • B01D5/0057—Condensation of vapours; Recovering volatile solvents by condensation in combination with other processes
  • B01D5/0072—Condensation of vapours; Recovering volatile solvents by condensation in combination with other processes with filtration
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D63/00—Apparatus in general for separation processes using semi-permeable membranes
  • B01D63/08—Flat membrane modules
  • B01D63/082—Flat membrane modules comprising a stack of flat membranes
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/02—Treatment of water, waste water, or sewage by heating
  • C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
  • C02F1/048—Purification of waste water by evaporation
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
  • C02F1/447—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by membrane distillation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2313/00—Details relating to membrane modules or apparatus
  • B01D2313/14—Specific spacers
  • B01D2313/143—Specific spacers on the feed side
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2313/00—Details relating to membrane modules or apparatus
  • B01D2313/22—Cooling or heating elements
  • B01D2313/221—Heat exchangers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2313/00—Details relating to membrane modules or apparatus
  • B01D2313/24—Specific pressurizing or depressurizing means
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2319/00—Membrane assemblies within one housing
  • B01D2319/04—Elements in parallel
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
  • C02F2103/08—Seawater, e.g. for desalination
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
  • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
  • Y02A20/124—Water desalination
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
  • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
  • Y02A20/124—Water desalination
  • Y02A20/131—Reverse-osmosis
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
  • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
  • Y02A20/20—Controlling water pollution; Waste water treatment
  • Y02A20/208—Off-grid powered water treatment
  • Y02A20/212—Solar-powered wastewater sewage treatment, e.g. spray evaporation

Definitions

• the present invention relates to a method for the purification of a liquid by membrane distillation, in particular for the production of desalinated water from seawater or brackish water or process water, and an apparatus for carrying out such a method.
• Membrane distillation differs from known distillation techniques such as multi-stage flash, multiple effect distillation and vapour compression in that a non-selective, porous membrane is used. This membrane forms a separation between the warm, vaporising retentate stream and the condensed product, the distillate stream.
• the pores are not wetted by the liquid; only vapour passes through the membrane.
• Membrane distillation was first described in US 3,334,186. The intention was to improve the efficiency of seawater desalination by the use of an air- filled porous hydrophobic membrane.
• the method concerned here was so-called direct contact membrane distillation: a warm seawater stream and a cold distillate stream are both in direct contact with the membrane.
• DCMD Direct contact membrane distillation
• AMD Air gap membrane distillation
• SGMD Sweeping gas membrane distillation
• VMD Vacuum membrane distillation
• the specific flux amounts to 1.30.10 10 m3/m2.s. Pa, at a relatively high mean velocity in the retentate channel of 0.09 m/s.
• Specific flux is defined as the distillate flow rate per unit membrane surface area, per unit water vapour pressure difference between the bulk of the retentate and feed streams.
• Air gap membrane distillation was first described in 1971 in GB 1 225 254 A. In addition to the use of an air gap, counter-current flow of feed and retentate (and thus recovery of latent heat), is already proposed. In addition, AGMD was described in 1982 in DE 3,123,409 (Siemens). This application relates to the use of a gap (with a thickness of 3 mm), filled with air, or optionally a lighter gas such as hydrogen, between a flat porous membrane and a cold condensation surface. The aim was to reduce the transport of perceptible heat by conduction through the membrane. It was established experimentally that heat transport by conduction was approximately equal to that by evaporation.
• European Patent Application 0 164 326 describes the use of an air gap with membrane distillation, the various features being constructed in the form of concentric tubes. A variant of this in which packets of flat membranes were used is described in the article "Design and field tests of a new membrane distillation desalination process (Desalination 56 (1985), pp. 345-354). It is striking that here the principle of counter-current flow of seawater and retentate is abandoned, as a result of which no recovery of heat of evaporation is possible. Energy consumption figures are then also not given.
• WO 8607585 A (1986) is based on the same model data which were used for above work, but deduces from these that an air gap thickness of 0.2 to 1.0 mm is needed in order to achieve both a high flow rate and a low loss of perceptible heat (target is 300 - 800 kJ/kg water). No account is taken in the model of temperature changes at and in the hot and cold walls, as a result of which a far too optimistic picture is painted.
• the aim of the present invention is, however, to achieve a breakthrough in the performance (specific flux, or distillate flow rate per unit membrane area per unit driving force) of direct contact membrane distillation and thus appreciably to reduce both the costs and the energy consumption of such a membrane distillation system.
• the present invention relates to a method for the purification of a liquid by membrane distillation comprising:
• the positive liquid pressure difference between the retentate stream and the feed stream at the corresponding points of the retentate channel and the feed channel is applied over at least 50% of the total length of each of the retentate channel and feed channel, and more preferably over at least 75% of the total length of each of the retentate channel and feed channel.
• the porous membrane has a thickness in the range of from 50 to 1000 ⁇ m.
• the porous membrane has a thickness in the range of from 100 to 600 ⁇ m, more preferably in the range of from 125 to 500 ⁇ m, and most preferably in the range of from 150 to 400 ⁇ m.
• the retentate channels are delimited by porous hydrophobic membranes (porosity greater than 70 % and preferably greater than 80 % and pore size smaller than 2.0 ⁇ m, preferably between 0.01 and 0.5 ⁇ m). It will be appreciated that porous hydrophobic membranes are not wettable by a liquid. Hence, only a vapour, no liquids, can pass through such membranes.
• the membranes concerned can be commercially available membranes made of materials such as PTFE, PVDF, PP and PE and the like.
• the porous membranes to be used in accordance with the present invention can be laminated with other materials (e.g. non woven materials of PP, PET etc), which protect the membranes against abrasion, and/or give mechanical support.
• asymmetric microfiltration and ultrafiltration membranes made of materials such as polyethersulphone, polysulphone, polyacrylonitrile, polyamides, etc. can also be used.
• the surface of these membranes it is preferable to make the surface of these membranes completely or partially additionally hydrophobic, for example by means of a coating or other surface modification.
• the retentate channels consist of flat membrane envelopes or hollow fibres or capillary membranes placed in parallel. The retentate flows through the inside of the envelopes or the lumen of these fibres/capillaries.
• the active layer of the membrane is on the retentate side.
• the retentate channels can also be formed by flat plate membranes or membrane sheets, optionally in a spirally wound configuration.
• the feed channels, through which the feed stream runs, are likewise preferably formed by flat envelopes or hollow fibres/capillaries made of either hydrophilic or hydrophobic material, placed in parallel.
• the walls of these channels are now non-porous, that is to say are not vapour-permeable or are barely vapour-permeable.
• said walls have a thickness typically between 10 and 2000 ⁇ m, preferably between 20 and 200 ⁇ m, either in sheet or fiber/capillary format. They can be made from polymeric materials (PP, PE, PET, nylons /PA, etc.; with or without filler-materials in order to e.g.
• the condenser material can be given such a shape that the resulting effective area for heat transfer is higher than the membrane area, e.g. by ribs, folds or other corrugations, by the use of a plurality of fibers / capillaries, etc.
• a spacer material is arranged in the feed channel.
• the entire feed channel is filled with the spacer material.
• a spacer material is arranged in the retentate channel.
• the entire feed channel is filled with the spacer material.
• inside the distillate channel also a spacer material can be arranged.
• the same type of spacer material or different types of spacer material may be applied in both the feed channel and the retenate channel a similar type of spacer material is applied.
• the spacer materials can suitably consist of nettings, technical fabrics and the like, made of woven or non woven filaments in various shapes, of polymers like PP, PE, EVA, etc. Suitable shapes include symmetrical squares, rectangles, diamonds, waves, etc.; also, asymmetrical shapes and filaments can be used. A preferred shapes of spacer material are non woven, diamond configurations .
• the discharge of the distillate stream can take place via hydrophilic or porous material (such as a fabric, or rods) that has been applied inside the distillate channel. It is also possible to keep the distillate channels empty from other material than the produced water itself, and to discharge the distillate stream by pressure (built during production of the distillate), or by gravity, or by suction.
• the method according to the invention can be implemented in a number of embodiments.
• use can be made of flat membrane sheets or plates, optionally in a spirally wound configuration, or plate-like structures consisting of multiple capillary-like channels, to limit the flow channels for the retentate stream.
• hollow fiber or capillary arrays can be used.
• the feed channels in which the to be purified feed flows in counter-current with the retentate stream, and for the distillate channels, through which the condensate (distillate) flows either in co-current or in counter-current or crossflow etc. with the retentate stream.
• These embodiments are usually constructed of several parallel envelopes or arrays of capillaries/hollow fibres, put together by suitable bonding techniques (pottings using suitable resins of epoxy, polyurethane etc; glues using e.g. polysiloxane, polyurethane, etc., either as one — or two/multi component formulations; hot melt materials; heat- or ultrasonic welding techniques; and all other techniques known to bonding experts.
• suitable bonding techniques pottings using suitable resins of epoxy, polyurethane etc; glues using e.g. polysiloxane, polyurethane, etc., either as one — or two/multi component formulations; hot melt materials; heat- or ultrasonic welding techniques; and all other techniques known to bonding experts.
• the feed stream to be heated flows in virtually ideal counter-current to the vapourising retentate stream and the condensate distillate stream flows in co-current with the retentate stream and/or in counter-current to the feed stream, by which means the sensible heat of the distillate stream is recovered into the feed stream.
• US 4,545,862 describes a method wherein in both a flat and (preferably) a spirally wound module is applied, using flat hydrophobic and thin PTFE membranes.
• the method was tested for salt water desalination.
• the distillate stream was separated from the seawater stream fed in counter-current to the vaporising retentate and the seawater stream, thus effectively absorbing the heat of condensation.
• two discharge options of the distillate stream i.e. both from the cold side of the module (entrance of feed, outlet of retentate) and from the hot side of the module (outlet of feed, entrance of retentate)
• performance (flux) of the module increased considerably when applying the first option.
• the present invention differs essentially from the above- mentioned and known method in that use is made of a positive liquid pressure difference between the retentate stream and the feed stream at the corresponding points of each of the retentate channel and the feed channel over at least part of each of the retentate and feed channels.
• the membrane will be pressed against the non-permeable condenser surface, or when applied against a distillate-discharging material placed between the condenser surface and the membrane.
• the condenser wall on its turn, will be pressed against the spacer material placed inside the feed channel. It is noted that in US 4,545,862 this configuration is not possible, as is shown in Figs.
• the feed channel contains a spacer material
• the condenser sheet material is pressed against this material by the positive liquid pressure difference between the retentate and feed channel, and by this a "milking effect" as described in US 4,545,862 essentially is not possible to obtain.
• the process according to the present invention cannot be carried out using the configuration as described in US 4,545,862.
• a further channel is arranged through which a fluid is passed, whereby a positive liquid pressure difference is applied between the retentate stream and the fluid stream.
• said fluid stream passes through the further channel in co-current direction with said retentate stream, and the fluid stream preferably comprises a residual heat stream (waste heat or heat derived from warm liquids, etc.).
• the further channel comprises non-permeable walls, through which a hot fluid can suitably be pumped co-currently with said retentate stream, at a fluid pressure equal or preferably slightly higher than that of said retentate stream, inducing an extra, and thus advantageous, pressure on the feed/distillate/retentate channels.
• This embodiment has the advantage that full use is made of the residual heat and that the driving force towards the inlet side of the feed stream is maintained by a rising temperature difference.
• the modules suitable for this can be of an extra compact and inexpensive construction.
• the distillate stream is discharged at the hot side of the distillate channel, thus in counter-current flow with the retentate stream.
• This variant has the advantage that hot distillate stream is produced, taking sensible heat away from the feed stream now flowing in co-current with the distillate stream, by which the feed stream can take up more latent heat, thus more vapour can be condensed, producing more distillate.
• the distillate stream is discharged at the hot side of the distillate channel. Thus, the distillate stream is discharged in counter-current flow with the retentate stream.
• said distillate stream can be introduced in the further channel that is arranged within the retentate channel as described hereinbefore.
• This embodiment has the advantages that more distillate is produced at a given feed stream flow, and that the sensible heat taken from the feed stream is co-currently transferred to the retentate stream, thus reducing the amount of heat which has to be introduced for vapour formation, resulting in a very attractive reduction in the energy consumption in the method.
• the present invention is particularly suitable for the desalination of seawater.
• Existing technologies for this such as multi-stage flash distillation and reverse osmosis, have been optimised to virtually the maximum extent and because of too high an energy consumption and too high a level of investment per unit product are too expensive compared with on-shore purification production techniques.
• By use of the present invention spectacular results are achieved in respect of a high flow rate, a low heat loss, a very low energy consumption, a high water recovery, good water quality and a breakthrough in water production costs.
• the method is suitable for use at relatively low temperature (low-grade heat, waste heat, solar heat collectors, etc.). A substantial improvement in energy efficiency is anticipated, especially in the case of small-scale application.
• the present invention also relates to an apparatus suitable for use in the method according to the present invention which apparatus comprises a segment comprising a feed channel in which a spacer material is arranged, a distillate channel and a retentate channel, whereby the segment has a first distribution chamber for a feed liquid to be supplied, a second distribution chamber located opposite the first distribution chamber for feed liquid to be discharged, a third distribution chamber for retentate stream to be supplied and a fourth distribution chamber opposite the third the third distribution chamber for the retentate stream to be discharged, whereby the segment is provided with a first pump for pumping the feed stream pressure into the segment and a second pump which is arranged downstream the second distribution chamber or downstream the heat exchanger for pumping out the retentate stream under higher pressure (related to the pressure inside the feed channels) into the heat exchanger and/or the distribution chamber of the retentate channels, the wall between the feed channel and the distillate channel comprises a condenser surface in the form of a non-porous membrane, and the wall between the
• the porous membrane has a thickness in the range of from 100 to 600 ⁇ m, more preferably in the range of from 125 to 500 ⁇ m, and most preferably in the range of from 150 to 400 ⁇ m.
• the apparatus comprises a number of segments (modules) as described hereinabove which are connected in parallel to one another.
• a first pump is suitably arranged upstream of the series of connected segments
• one or more further pumps is (are) suitably arranged downstream the series of connected segments or in between the respective segments that are connected to each other.
• one or more pumps can be applied in between the respective segments that are connected in parallel to each other, in order to control more accurately the pressures inside the retentate channels versus the pressure inside the feed channels.
• a further channel is arranged through which a fluid is passed, whereby the liquid pressure of the fluid stream is equal to or higher than the liquid pressure of the retentate stream.
• said fluid stream passes through the further channel in co-current direction with said retentate stream, and fluid stream preferably comprises a residual heat stream.
• the further channel comprises non-permeable walls, through which a hot fluid can suitably be pumped co-currently with said retentate stream, at a fluid pressure equal or preferably slightly higher than that of said retentate stream, inducing an extra, and thus advantageous, pressure on the membrane/distillate/condenser channels.
• from one or both sides of the segments from one or both sides of the segments
• a pressure can be applied which is equal to or higher than the fluid pressure of the retentate stream.
• an additional pressure can advantageously be induced on the membrane/distillate/condenser channels.
• Said additional pressure can be established by using a means at one or both sides of the segmen(s) to be used, of which means the volume can be increased by introducing into said means a suitable fluid (e.g. an oil, water, air or another gas).
• a suitable fluid e.g. an oil, water, air or another gas.
• a balloon-type of structure can be obtained at one or both sides of the segment(s), which pressurised structure brings about the additional pressure on the membrane/distillate/condenser channels. It will be understood that such means will usually be made of a flexible material.
• FIG 1 a plurality of parallel placed channels and materials called “module” is depicted according to the invention.
• the module is divided into a cold side C and a hot side H.
• a relatively cold feed stream 1 is pumped with feed pump IP into the parallel feed channels 2, at the cold side C.
• These feed channels are constructed by the non-porous walls 3 and a spacer material 4.
• the feed stream is heated by taking up heat from the warmer distillate channels 5 at the other side of the walls 3. So, gradually the feed stream becomes hotter and leaves the module as stream 6 at the hot side H, with the aid of pump 6P.
• This pump ensures by suction that the pressure in the feed channels 2 is relatively low; typically between 0.1 and 3.0 bara (absolute pressure).
• the relatively hot feed stream 6 is pumped into a heat exchanging device 7, where it is heated further by an external heat input 15, (the heat used can be waste heat, solar heat, steam, hot solid material, etc.), and leaves the device as relatively hot retentate stream 8.
• Stream 8 enters the module at the hot side H, and flows through the parallel placed retentate channels 9 in more or less counter-current flow with stream 1.
• the retentate channels 9 are constructed by the vapour -permeable membranes 10 and the spacer material 11. In these retentate channels, the retentate stream 8 gradually becomes cooler because of evaporation of water vapour, and some heat conduction, through the membranes 11 into the distillate channels 5, where the water vapour condenses forming a pure, liquid distillate 13.
• the distillate channels are delimited by a membrane 10 at one side and a non- porous condenser wall 3 at the other side. Inside channels 5, a spacer material 12 can be placed. However, this is not strictly necessary in all applications of the present invention.
• the released heat in the distillate channels 5 is mostly transferred through walls 3 into the feed stream 1, flowing in the feed channels 2.
• the liquid distillate leaves the module preferably at the cold side C, by which also sensible heat of stream 13 is recovered and transferred into stream 1. It can, however, also be discharged at both sides C and H of the module. This discharge can take place by gravity, pumping, and/or by pressure build up inside channels 5 as a result of the water produced.
• the relatively cool and concentrated retentate stream leaves the module at the cold side C as stream 14.
• the absolute liquid pressure inside the retentate channels 9 is higher than in the corresponding feed channels 2.
• Typical absolute liquid pressures in the retentate channels range between 1.0 and 4.0 bara.
• a second embodiment of the invention is shown. This embodiment differs from the one shown in Figure 1 by way of the introduction of a fourth type of channels 17 inside the retentate channels 9. Inside these channels 17, the liquid pressure is preferably equal or higher than the pressure inside the corresponding part of channel 9. This can be established by entering a fluid 16 (liquid or gas or dispersion, etc.) inside these channels 17.
• fluid 16 has a temperature equal or higher than the retentate stream 8 flowing co-currently through channels 9, thus passing heat to stream 8.
• Channels 17 are constructed by two non-porous, heat-conductive walls 20, made of similar (but not necessarily the same) material as the walls 3, and a spacer material 18.
• Figures 3 and 4 show a third embodiment of the invention, respectively without and with a fourth channel, differing from the embodiments shown in Figures 1 and 2 in that the distillate stream 13 is discharged exclusively at the hot side H of the module.
• a fourth embodiment of the invention is shown, differing from Figures 2 and 4 in that the fluid which is pumped into the fourth channels 17 is the distillate stream 13 itself, which is discharged at the hot side H of module according to the third embodiment described above.
• Said fluid (distillate stream 13) is preferably heated further in a heat exchanging device 21, using a heat input 22 (both can be the same as device 7 , respectively heat input 15), and subsequently pumped as heated distillate stream 23 (using if needed pump 23P) into the channels 17. Doing so, most of the heat of stream 23 is transferred to the retentate channels 9, and the cooled distillate leaves the module at the cold side C as stream 24. Examples
• a membrane distillation module was constructed using 6 PET sheets of thickness 75 ⁇ m, width 0.50 m, length 1.50 m, and a polypropylene spacer material of thickness 2 mm to form 3 condenser envelopes, thus 3 feed channels . Further, 4 sheets of porous expanded PTFE (porosity 80%, thickness 120 ⁇ m) of similar size were used to form 2 membrane envelopes, within which envelopes 2 extra waste heat channels (the "further channels" 17 of Figure 2) were placed using 4 additional PET sheets and two PP spacer materials of 0.8 mm thickness.
• Example 2 The same module and process conditions as applied in Example 1 were used, only the feed flow was increased to obtain a mean flow velocity in the retentate channels of 0.06 m/s.
• P- feed 1 2.35 bara
• P-feed 6 2.25 bara
• P-retentate 8 2.05 bara
• P- retentate 14 1.14 bara.
• a specific flux of 1.25 .1O 10 m 3 /m 2 .s. Pa was measured.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Water Supply & Treatment (AREA)
• Environmental & Geological Engineering (AREA)
• Life Sciences & Earth Sciences (AREA)
• Hydrology & Water Resources (AREA)
• Organic Chemistry (AREA)
• Health & Medical Sciences (AREA)
• Toxicology (AREA)
• Sustainable Energy (AREA)
• Sustainable Development (AREA)
• Separation Using Semi-Permeable Membranes (AREA)

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• 2006
  • 2006-10-31 EP EP06076956A patent/EP1925355A1/en not_active Withdrawn
• 2007
  • 2007-10-31 WO PCT/NL2007/050524 patent/WO2008054207A1/en active Application Filing
  • 2007-10-31 JP JP2009534522A patent/JP5036822B2/ja not_active Expired - Fee Related
  • 2007-10-31 NZ NZ576854A patent/NZ576854A/en not_active IP Right Cessation
  • 2007-10-31 PL PL07834654T patent/PL2094376T3/pl unknown
  • 2007-10-31 CA CA2667758A patent/CA2667758C/en not_active Expired - Fee Related
  • 2007-10-31 EA EA200970430A patent/EA016271B1/ru not_active IP Right Cessation
  • 2007-10-31 US US12/447,304 patent/US8287735B2/en not_active Expired - Fee Related
  • 2007-10-31 ES ES07834654T patent/ES2388882T3/es active Active
  • 2007-10-31 EP EP07834654A patent/EP2094376B1/en not_active Not-in-force
  • 2007-10-31 KR KR1020097010835A patent/KR101505208B1/ko not_active IP Right Cessation
  • 2007-10-31 BR BRPI0718212-0A patent/BRPI0718212A2/pt not_active IP Right Cessation
  • 2007-10-31 CN CN2007800405665A patent/CN101600492B/zh not_active Expired - Fee Related
  • 2007-10-31 AU AU2007314728A patent/AU2007314728B8/en not_active Ceased
  • 2007-10-31 SI SI200731004T patent/SI2094376T1/sl unknown
  • 2007-10-31 MX MX2009004559A patent/MX2009004559A/es active IP Right Grant
  • 2007-10-31 PT PT07834654T patent/PT2094376E/pt unknown
  • 2007-10-31 DK DK07834654.1T patent/DK2094376T3/da active
  • 2007-10-31 MY MYPI20091751A patent/MY148839A/en unknown
• 2009
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  • 2009-05-06 ZA ZA200903124A patent/ZA200903124B/xx unknown
  • 2009-05-21 MA MA31908A patent/MA30913B1/fr unknown
• 2012
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